Google declined to comment and Yahoo did not respond immediately, CNN reported.

The majority of passwords were from the Netherlands, followed by Thailand, Germany, Singapore, Indonesia and the United States, which accounted for 859 reports from machines and 1,943 passwords, according to Trustwave.

In all, just over 100 countries were affected, and Trustwave said this shows the attack is "fairly global."

In compiling the data, Trustwave also discovered that many users are doing just what computer specialists advise against - using simplistic passwords that can easily be guessed.

For instance, the top five passwords Trustwave found in researching the breaches were: 123456, 123456789, 1234, password and 12345.